1. Field of the Invention
The present invention relates to a method of collecting methane hydrate gas hoarded in the bottom of the sea or in the bottom of the water, and an apparatus therefor.
2. Description of the Prior Art
Various methods have heretofore been studied for collecting methane hydrate gas. There has been known, for example, a method according to which hot seawater is injected into a methane hydrate layer in the bottom of the sea to change the temperature condition for the methane hydrate into a temperature at which the methane hydrate is decomposed into water and a methane hydrate gas, and the decomposed methane hydrate gas only is transported to a liquefying facility on the sea and is liquefied. There has further been known an apparatus for collection wherein a pair of transport pipes are extended from the facility on the sea to the methane hydrate layer, the seawater is injected into the methane hydrate layer through one transport pipe, and the other transport pipe is connected to the liquefying facility to collect the methane hydrate gas. As is well known, the methane hydrate is a product having a composition CH.sub.4. 6 to 7 H.sub.2 O and having affinity to water, and decomposes under a pressure of 8 kg/cm.sup.2 at 0.degree. C. producing heat of decomposition of 100 kcal/kg. However, it is difficult to correctly probe the pressure in the methane hydrate layer and the degree of stability of the layer from above the water or the sea. The transport pipes that are carelessly driven causes the methane hydrate gas to erupt on a large scale permitting a useful gas resource to be released into the open air accelerating the warming-up of the atmosphere.
Therefore, a technical problem is arousing that must be solved for trapping the methane hydrate gas on the bottom of the sea or on the bottom of the water using a flexible sheet. It is a first object of the present invention to solve the above-mentioned problem.
Another object of the present invention is to collect the methane hydrate gas trapped in the sheet by transporting it to above the water or the sea.